The 24-hour lithium level as a prognosticator of dosage requirements: a 2-year follow-up study.

The authors have previously described a technique whereby individual lithium dosage requirements can be predicted from 24-hour blood samples. Further experience over a 2-year period has shown the predictions to be reproducible over time. A micromethod for lithium determination is described, as are several cases in which aberrant results were found to indicate inadequate laboratory techniques or patients' failure to take medication. Because the technique reveals immediately those patients at the extremes of dosage ranges, toxicity and the need for frequent sampling can be avoided.